A Single Device for Mechanical and Radiation Quality Assurance (QA) Measurements of Medical Accelerators

Purpose: To develop a single unifying device that will record, document and track mechanical, optical and dosimetric measurements to reduce the number of devices used and time spent to perform the monthly Quality Assurance (QA) tasks recommended in AAPM Task Group 142 Report.

Methods: This device includes a novel multi-mirror system with rotating capabilities which directs the optical and radiation sources to a stationary camera to acquire images of all planes centered on the isocenter of the medical accelerator. A single phosphor screen is used as the receptor for optical light imaging. A plastic buildup sheet is added for radiation measurements. A computer interface allows efficient pass/fail analysis for laser alignment, light/radiation field coincidence, flatness and symmetry tests and MLC QA.

Results: The system has been used to successfully acquire images that have never been recorded before, such as a combination of the light field, optical distance indicator and lasers as well as radiation field. QA of mechanical motions such as table rotation is readily captured. Radiation QA measurements accommodate both x-ray and electron beams. QA of gantry motion can be performed by rotating the device. The time spent in Monthly QA according to TG-142 for these tasks will be reduced in half.

Conclusion: A single device has been successfully developed to unify all mechanical, optical and radiation components for required and recommended monthly QA tasks, reducing monthly machine maintenance time. In particular, the device records and documents optical measurements that are now only evaluated visually which will strengthen the confidence for safe patient treatment.

Funding Support, Disclosures, and Conflict of Interest: Dr. John W. Wong is a founder of JPLC Associates LLC which has licensed the technology from Johns Hopkins University.
Dr. Daniel J. Mirota's participation in this publication was as a paid consultant for JPLC Associates LLC. All opinions expressed and implied by Dr. Daniel J. Mirota in this publication are solely those of Dr. Daniel J. Mirota and do not represent or reflect the views of Johns Hopkins University.
The work is supported in part by a grant from Technology Development Corporation (TEDCO) of Maryland.